The present invention pertains generally to remote sensors and more particularly to electromagnetic intrusion sensors.
In recent years the use of remote sensors to alert friendly forces to the presence of enemy personnel or vehicular traffic has become widespread. The sensor type which had the lowest cost and has been most commonly employed to date is the seismic sensor. Although these devices have proven to be very useful, they tend to exhibit a high false alarm rate under certain terrain and environmental conditions. Also, their effective range varies widely depending on the surface geology of the implantation site. Magnetic sensors have also been successfully employed and have exhibited very low false alarm rates. However, the range of magnetic devices is quite limited and they only respond to the presence of ferrous metals (which may be advantageous in some application). Both seismic and magnetic sensors are passive devices in that they detect the presence of energy generated by a target. This results in low power drain.
An electromagnetic sensor is an active device which senses the influence of a target on the electromagnetic field generated by the sensor. Its detection range is intermediate between the maximum and minimum range of seismic sensors, and is less influenced by conditions at the implantation site resulting in a low false alarm rate. However since they are active devices they have a high power drain resulting in short term use only at remote sites.